Hydro-pneumatic system with pressure limiting valve
A hydro-pneumatic system has an air powered motor driving a hydraulic pump with a pressure limiting valve that turns off air flow to the air motor when a hydraulic pressure output by the pump at a sense port of the valve reaches a certain limit. A valve element of the valve has spring, hydraulic and pneumatic sections, with an unbalanced area of the hydraulic section in a sealed pressure chamber of a cartridge that is part of the valve housing. The pneumatic section extends out one end of the cartridge to fill a bore between the air inlet and outlet ports when the pneumatic section is extended, and allow air to pass when it is retracted.
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This application is a divisional of U.S. patent application Ser. No. 12/446,611, filed Dec. 3, 2009, which is a national stage entry under 35 U.S.C. §371 of International Patent Application No. PCT/US2007/082504, filed Oct. 25, 2007, which claims the benefit of U.S. Provisional Patent Application No. 60/863,078, filed Oct. 26, 2006, the entire contents of all of which are hereby incorporated by reference.
FIELDThis invention relates to hydro-pneumatic systems and, in particular, to such a system having a hydraulically actuated pneumatic valve.
BACKGROUNDHydraulic systems exist having pumps that are driven by compressed air driven motors. The peak hydraulic pressures generated by the pump are generally significantly greater than the pneumatic pressure used to drive the pump, but in many applications the peak hydraulic-pressure obtainable is limited by the pneumatic pressure used to drive the pump and the operation of the pump relies on the pump stalling when that pressure is reached. In some of these pumps, the pneumatic motor will never stall due to leakage, losses, system design or pressure variation in the system. Particularly for these kinds of applications, some other means is desirable to cause the pneumatic motor to stop at a given limit of hydraulic pressure.
SUMMARYThe present invention provides a hydraulic system with a pressure limiting valve that is hydraulically actuated to turn off the flow of air to the pump drive motor at a certain hydraulic pressure limit. The valve has a valve housing having an air inlet port and an air outlet port and a hydraulic fluid sense port. A valve element in the housing has a hydraulic section and a pneumatic section, the hydraulic section being in fluid communication with the hydraulic sense port and the pneumatic section being in fluid communication with the air inlet port and the air outlet port. The valve element is operable to open fluid communication between the air inlet port and the air outlet port in an open position of the pneumatic section and to close fluid communication between the two air ports in a closed position. The hydraulic section has an unbalanced area in fluid communication with the hydraulic fluid sense port that moves the valve element when a pressure in the hydraulic fluid sense port reaches a certain limit.
In preferred aspects, a spring urges the pneumatic section to the open position, and the spring force is preferably adjustable. In another aspect, the hydraulic section and the pneumatic section of the valve element are integral with one another, and a cartridge portion of the housing defines a hydraulic chamber in which the unbalanced area of the hydraulic section resides. The valve element can extend out of the cartridge at one end to a position in which it can close communication between the two air ports, and at the other end of the cartridge, can extend out of the cartridge to be acted on by a biasing spring.
These and other objects and advantages of the invention will be apparent from the detailed description and drawings.
Referring to
Valve element 26 extends leftwardly from, the cartridge 16 to a spring portion 38 surrounded by a compression spring 40 that is compressed between axially facing surface 42 of body 14 and a spring reaction member 44 that is threaded on the end of spring section 38 of the valve element 26. Turning the element 44 relative to the valve element 26 either compresses the spring more in one direction, or relieves the compression on the spring 40 in the other direction to adjust the amount of spring biasing force on the element 26, which force biases the element 26 to move the pneumatic section 32 into the open position.
Hydraulic fluid introduced to the hydraulic fluid sense port 22 acts on the unbalanced area 30 in the chamber 24. Unbalanced area 30 is created by a difference in diameter in the element 26 that occurs between sliding seals 54 and 56, that creates a shoulder at the junction between the two diameters, identified at 30 in
Referring to
A preferred embodiment of the invention has been described in considerable detail. Many modifications and variations to the embodiment described will be apparent to those skilled in the art so the invention should not be limited to the embodiment described.
Claims
1. A method of operating a hydraulic system, the hydraulic system including a hydraulic pump in communication with a source of hydraulic fluid and operable to draw fluid from the source of hydraulic fluid and deliver the fluid under a supply pressure, an air motor in communication with and powered by a source of compressed air and operable to drive the hydraulic pump, and a pressure limiting valve including a valve housing having an air inlet port in communication with the source of compressed air, an air outlet port and a hydraulic fluid sense port, and a valve element movably supported in the housing and having a hydraulic section in fluid communication with the hydraulic fluid sense port and a pneumatic section in fluid communication with the air inlet port and the air outlet port, the method comprising:
- applying a pressure from the hydraulic pump to the hydraulic fluid sense port;
- when the pressure is below a pressure limit, positioning the valve element in an open position to provide fluid communication between the air inlet port and the air outlet port; and
- when the pressure is at the pressure limit, moving the valve element toward a closed position to close fluid communication between the source of compressed air and the air motor.
2. The method of claim 1, wherein the hydraulic section has an unbalanced area, and wherein applying includes acting on the unbalanced area.
3. The method of claim 1, wherein applying includes applying the supply pressure to the hydraulic fluid sense port.
4. The method of claim 3, wherein the hydraulic section has an unbalanced area, and wherein applying includes acting on the unbalanced area with the supply pressure.
5. The method of claim 1, wherein the valve includes a spring, and wherein positioning includes urging the valve element toward the open position with the spring.
6. The method of claim 5, further comprising adjusting a force applied by the spring to the valve element.
7. The method of claim 5, wherein the valve element has a spring section, and wherein urging includes acting on the spring section with the spring.
8. The method of claim 5, wherein moving includes overcoming a force applied by the spring.
9. The method of claim 1, wherein moving includes moving the pneumatic section into a position between the air inlet port and the air outlet port to block a flow of air between the air inlet port and the air outlet port.
10. The method of claim 1, further comprising, when the pressure is above the pressure limit, maintaining the valve element in the closed position to close fluid communication between the air inlet port and the air outlet port.
11. The method of claim 1, wherein the hydraulic section and the pneumatic section of the valve element are integral with one another.
12. The method of claim 1, wherein the valve housing includes a valve block and a cartridge portion, the cartridge portion defining a hydraulic chamber in which an unbalanced area of the hydraulic section resides.
13. A method of operating a hydraulic system, the hydraulic system including a hydraulic pump in communication with a source of hydraulic fluid and operable to draw fluid from the source of hydraulic fluid and deliver the fluid under a supply pressure, an air motor in communication with and powered by a source of compressed air and operable to drive the hydraulic pump, and a pressure limiting valve including a valve housing having an air inlet port in communication with the source of compressed air, an air outlet port and a hydraulic fluid sense port, and a valve element movably supported in the housing and having a hydraulic section in fluid communication with the hydraulic fluid sense port and a pneumatic section in fluid communication with the air inlet port and the air outlet port, the method comprising:
- applying the supply pressure from the hydraulic pump to the hydraulic fluid sense port;
- when the pressure is below a pressure limit, positioning the valve element in an open position to provide fluid communication between the air inlet port and the air outlet port; and
- when the pressure is at the pressure limit, moving the valve element toward a closed position to close fluid communication between the source of compressed air and the air motor.
14. The method of claim 13, wherein the hydraulic section has an unbalanced area, and wherein applying includes acting on the unbalanced area with the supply pressure.
15. The method of claim 13, wherein the valve includes a spring, and wherein positioning includes urging the valve element toward the open position with the spring.
16. The method of claim 15, further comprising adjusting a force applied by the spring to the valve element.
17. The method of claim 15, wherein moving includes overcoming a force applied by the spring.
18. The method of claim 13, wherein moving includes moving the pneumatic section into a position between the air inlet port and the air outlet port to block a flow of air between the air inlet port and the air outlet port.
19. A method of operating a hydraulic system, the hydraulic system including a hydraulic pump in communication with a source of hydraulic fluid and operable to draw fluid from the source of hydraulic fluid and deliver the fluid under a supply pressure, an air motor in communication with and powered by a source of compressed air and operable to drive the hydraulic pump, and a pressure limiting valve including a valve housing having an air inlet port in communication with the source of compressed air, an air outlet port and a hydraulic fluid sense port, a valve element movably supported in the housing and having a hydraulic section in fluid communication with the hydraulic fluid sense port and a pneumatic section in fluid communication with the air inlet port and the air outlet port, and a spring, the method comprising:
- applying the supply pressure from the hydraulic pump to the hydraulic fluid sense port;
- when the pressure is below a pressure limit, positioning the valve element in an open position to provide fluid communication between the air inlet port and the air outlet port, positioning including urging the valve element toward the open position with the spring;
- when the pressure is at the pressure limit, moving the valve element toward a closed position to close fluid communication between the source of compressed air and the air motor, moving including overcoming a force applied by the spring; and
- adjusting a force applied by the spring to the valve element to adjust a value of the pressure limit.
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Type: Grant
Filed: Feb 14, 2014
Date of Patent: Nov 4, 2014
Patent Publication Number: 20140161636
Assignee: Actuant Corporation (Menomonee Falls, WI)
Inventors: Frantz D. Stanford (Monona, WI), Bruce E. Knuth (Oconomowoc, WI), Kay Lap Gilbert Chan (Madison, WI)
Primary Examiner: Peter J Bertheaud
Application Number: 14/181,195
International Classification: F04B 35/00 (20060101); F04B 35/02 (20060101); F16K 31/12 (20060101); F16K 31/36 (20060101); F16K 31/122 (20060101); F15B 11/072 (20060101);